Abstract: A roller cam follower, especially an engine hydraulic roller lifter, is restrained from rotation away from a position in which the roller rotates squarely on its associated cam by a retainer clip fixed on the lifter body and having a tang with flat sides engaging an axial groove in an associated bore of the engine lifter gallery. The retainer clip is a closed ring with opposite flexible hat sections connected by arches having inner edges that snap into a groove on the lifter body. The inner edges are preferably angled upward to aid installation and the hat sections preferably have squared inner ends that engage flats on the lifter body to prevent relative rotation of the body and clip.

Abstract: A camshaft has, for each valve lifter, a high lift cam between two low lift cams, the high lift cam fitting within the envelope of the low lift cams. The lifter comprises an outer tappet elongated in the direction of the camshaft and slidably mounted in an elongated bore in a cam carrier. The outer tappet is contacted by both low lift cams and operates two valves simultaneously. An elongated bore extending transverse of the outer tappet carries an elongated inner tappet which is contacted by the high lift cam. A hydraulically actuated locking mechanism couples the tappets for movement together for high lift operation and unlocks for low lift operation to allow the inner tappet to idle in the outer tappet.